According to a photograph by Đuro Griesbach from 1939, there was a vertical sundial on the southeast facade of the church.

References:

1. Griesbach, Đuro. Church of St. Catherine (Krapina): portal, niches with sculptures of St. Joachim and Anne. 1939. Schneider's photographic archive, Digital collection and catalogue of the Croatian Academy of Sciences and Arts
2. Reberski, Ivanka (ed.). Krapina-Zagorje County: sacral architecture with inventory, feudal architecture, memorials, Institute for Art History – Školska knjiga, Zagreb, 2008, p. 322.